Multiplex signaling system



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May 15, 192s. 1,669,449

- A s. BRAND MULTIPLEX S IGNALING SYSTEMA l Filed May 1, 1926 sSheets-sheet 2 A TTORNEY May 15, 1928,. y 1,669,449

- S. BRAND MULTIPLEX S IGNALING SYSTEM /NI/ENTR /I TTU/CNE Y PatentedMay 15, 1928.

UNITED ISTATES .itA

SMART BRAND, OF- BROOKLYN, NEW YORK, AssIGNon 'ro AivinnrcAN TELEPHONEAND rntnenarn COMPANY, A CORPORATION or NEW'YORK.

MUL'rrPLEx srGNALINe sYsTEM.

Application filed May 1,

it is au obiect of my invention to provide apparatus and a method formultiplex can rier cur-rent signaling. Another object of my inventionisV to provide a system adapted for receiving by the aid of locallyproduced currents in proper synchronism and phase relation with4 thereceived currents. In a more limited aspect, myinvention relates to'providing such currents at the receiving end this specification by wayof example. It

will'be understoodA that the following description relates moreparticularly to these embodiments of the invention, and that the scopeof the invention is to be determined phase of. the current componentcontrolled from the `appended claims.

4Referring tothe drawings, Figure 1 is a vdiagram of transmittingapparatus adapted for sending two phase-distinguished messages on eachfrequency of a multiplex carrier current system. IFig. 2' is Va diagramshowing corresponding receiving apparatus. Figz is a diagram givingdetails of the receiving network and signal compensator shownsymbolically in Fig. 2. Figs. 4, 5 and 6 arediagrams of respectivealternative receiving apparatus.

Referring to the transmitting apparatus shown in Fig. l, the oscillator21 generates an alternating current of fundamental frequency which isdeliverd to the harmonic generator 22 whose Output may be madeconveniently to comprise various odd harmonics of the said fundamental.This composite output current is put on the conductors 23, vand thevarious harmonics are passed re`* spectively by the band filters 24 inmultiple. The current of single harmonic frequency from each band lter24 goes to a respective phase splitter PSp from which two outputcurrents of the same frequency butfo apart in phase are transmitted andsuperposed in the inputv of a band filter 25. Each of these two currentcomponents is controlled for signaling by a respective key K, or K3. Theoperation of such a key reverses the thereby. The two currents of thesame frequency, 90 apart in phase, and each ref ter 28.

192e. serial No. 106,100.

vversed in phase from time to time by a ychange from markingto spacing`or fromv spacing to marking by its respective key, are superposed andpassed through the band r filter' 251and put onv the conductors 26 andvfilters 24 and .put throughV phase ysplitters PSp and sending networkSN like those already described. .The output currents from such sendingneworks are put through respective band'filters 25l and superposed onthe line L.

At the receiving station shown inFig.` 2, the currents go from the lineL to conductors 27 vand thence to respective band iilterssuch as 28 and39 in multiple.4 rIhese band filters pass the respectiveliarmonicfrequencies corresponding to theV vband filters 24 and 25 at the sendingend. One of these harmonic frequency currentsis passed by the band fil-Through the conductor `pair 30 the output currents from thisfilter havetheir electromotive forces lapplied' alike to .the grids of the twodetectors 3l and 32. 1

Bymeans presently to be described, acurrent is generated locally of thesame frequency as that passed by the band filter 28,

and this local current is supplied over the conductor pair 36 to theadjustable phase plied respectively across the grids and filaments ofthe detectors 31 and 32.

`Of the two 90D components received over of the detector 3l, but one ofthem will be in phase (or in phase opposition) with the locally suppliedcurrent over the conductors 37, and the other 90 component will be inquadrature. rllhis statement is based on the assumption that the phaseshifter '35 is given afproper adjustment. ponent will be effective inthe detector output circuit, and the polar relay 33 will accordinglyindicate the phase reversals on` Only the first cointhis one componentas determined by the corresponding key K1 at the sending end."

Similarly, the message signals on the other 90o component will beindicated by the relayk 34 associated with the remaining detec-lAccordingly, the output from this modulator 57 will also comprisea'component current of frequency p which is passed by the low passfilter 59 to the harmonic generator 60. The output from this harmonicgenerator comprises all the harmonics of the fundamental frequency p, asat the sending end. These are amplified by the amplifier 61 and dis-`tributed to the various phase splitters and receiving networks in themanner heretofore described.

The modulator 57 may be so designed and arranged that third order termswill be present in its output. In this case, the switches 103 and 103may be opened, and 104 closed; thus there will be no feed-back, but thecurrent of frequency p will be found amoung the modulation outputcomponents and will be sifted through the low pass filter 59, and therest of the operation will be as described with the switches in thepositions shown in Fig. 4.

Another modification is shown in Fig. 5. In this case, the two receivedcarrier current components of frequencieslnp and 211.101: p are siftedout from the receive'dcurrent by respective band filters and superposedon the input of the oscillating audion 105. The associated tuned circuit106 is tuned as nearly as practicable to the frequency p as determinedat the sending end, so that the audion 105 naturally oscillatesapproximately at this frequency.

The adjustment of the tuned circuit 106 could not be made accuratelykenough to keep the oscillator 105 in precise synchronism and phaserelation with the fundamental current of frequency p at the sending end.When 'an oscillator is tuned approximately to a certain frequency, thenif a current of that frequency or a simple harmonic thereof issuperposed in its input, it will hold the oscillator exactly in step atthe intended frequency. If there is only one harmonic current applied inthe input, it will give assurance that the frequency of the oscillatorwill be held at the same frequency as the fundamental lof the Saidharmonic, but different phase relations between-the oscillator outputfrequency and the said fundamental will be possible.

By applying two different harmonic lcomponents such as 'ftp and Qnpip tothe input of the oscillator of approximate natural frequency p, it isforced by both of them and is not only synchronized to the fundamentalin respect to frequency, but also is brought into a unique phaserelation with the fundamental corresponding to the said two harmonies.Hence, the output current of frequency p from the oscillator 105 is inproper phase relation with the fundamental cur-A rent of frequency p atthe sending end, and whenever the system is started up after asuspension of operation, this output current of frequency p willbegenerated in proper phase. It is put through theharmonic generator 107and its output vharmonic components are supplied to respective phase qsplitters and receiving net-Works'for the 70 system, as described forFigs. 2 and 4.

Another modification is shown in Fig. 6. Here, as in Fig. 5, the tworeceived currents of frequencies np and Qnpip are'filtered andsuperposed in the modulator 108 correy sponding to the dotted line box108 of-Fig. 5. The output ycurrent offrequency p from the modulator'108of Fig. 6 is applied op,- positely to the grids of the detectors 109 and109.

The oscillator 110 has the condenser of its oscillating circuit at 111,and another .condenser 111 'is provided which may be connected inparallel with 111 by the closure of the switch 112. With the switchopen, the oscillator 110 is tuned slightly above Vthe frequency p, butwith the switch 112 closed, the timing is slightly below the frequencyp. The output from the oscillator 110 goes to the'harinonic generator113, and the harmonics are distributed thence to the phase splitters andreceiving networ rs, as heretofore described.

Bridged across the output from the oscillator 110 is a filter LF thatpasses the cur- 95 rent of frequency p over conductor 114and` superposesthe corresponding electromotive force alike on the grids of thedetectors 109 and 109. When these two inputs via 108 and 114 are inquadrature, the detector out- 100 `put circuit relay will hold itsarmature 112v at neutral, but when the input at 114 gets a little aheadof the o relation with the input from 108, the armature at 112 willclose and slow down the oscillator until the 105 quadrature rela-tion isrestored, when it will open again. Thus it will he seen that thearrangement of Fig. 6 provides a local oscillator 110 of approximatelythe fundamental frequency p which is held closely to that 119 frequencyby a current of exactly that frequency derived from two harmonicsthereof received over the line.

The voltmeter relay 201 operates when the departure from the quadraturerelation be 115v comes excessive. As shown in Fig. 6 it produces acomparatively slow stepped motion of wheel 202 so as to adjust condenser111 which is in parallel with 111. By the voltmeter relay 201, thecapacity of the com- 1,20 bined condensers 111 and 111 is kept close toits proper value, and then by means of condenser 111 and switch 112 asupplemetai fine adjustment is made.

I claim:

1. In multiplex carrier current signaling with the generation ofcurrents of the carrier frequencies at the receiving end, the methodwhich consists in modulating together two received carrier currents, and13 from the modulation product, filtering ont a current of fundamentalfrequency ot' which the carrier `frequncies are harmonics, and`determiningthereby thei'i'eqnencies and phase :relations of theVcurrentsgenerated the receiving end. l i i l 2.In inultiplexcarriercurrent signaling With the generation of currents of respective carrierfrequencies at the receiving end,

the .method of `ffieiiring delinite syiiiclno nisn'i andpliasefi'clationl hetnfeeneach ref ceived; currentand the i respectivecurrent generated at the receiving; end, which consstsin selecting twoofthe received currente having a prime harmonie relation to each otherand `applying them both to effect synchronisinwhercby `all `the currentsare synehronized respectively at,v definite phase relations.` i p3.,'l`he method `of controlling the generation of one alternatingeuri'ent byV another, which consists ,in applying two dili'crentselected `harmonics of the one current to `force `the generationof theother current in `definite synchronisni and phase relation,

4i.` The method of `controlling the generation of a set `of currents allharinoniesot a certain, fundamental, which consiste in a'pplying two`different selected `harmonics of another corresponding setto hold themall in` respective synchronisin and denite phase f relation.

5. The inetliodof` synchonizing the output of a` Vacuum tube oscilla-tor'with a giveny alternatingcurrent, which consists in super# posing inithe `oscillator input two diilerent p selected harmoniesl of. the; saidgiven current.

`it to operate at thewfrquncyfof the Said generator. i i v i to controlthe other generator.

ceived coinponentjcarrier lcnrnents and ingiearie ,i

tonpply tivoot `the `said received ,carrier currents` to synchronizelsaid first mentioned ineens Wherebythe entire set of locallygenf eratedcurrents will befde'tinitely synchro? nized with the correspondingreceiyedfcuirents` respectively,

p ,In combination, an alternating` euri-'ent generator, nieansvtoproduce harmonie our rents, a vacuum tube oscillatorand means`V tosujliierpose` two of u the said harmonic, cui? rents` in the inputofsaidoscillator to force 8. In combination, tfvvo-l alternating cuir?- rentgeneratorsliof approximately A,the ,saine natural `frequency, `andnieanslftojliold them in definite synchronisin and phase relation by theapplication of two selectedharmonics of the current:froinwone generatorapplied 9.".111` combination, an,` alternating impressing onV the`second ygenerator two seu `u`r` rent generatoigmineans tolproduceharmonic currents, asecond generator, and means Jfor lected `harmonicsof the current of vthe ret l generator to canse ittoy yield asits fiinda` linental the difference of the frequencies, of

the two selected harmonics.

In testimony whereof, signediny nanie` to this, .e specification this219th" day of Api-11,1926. f Y .SMARTBRANQ-

